The present invention relates to a system for increasing the spatial resolution of a video.
The resolution of a typical liquid crystal display is approximately 720×480 which is on the order of standard definition television. The resolution of a typical high resolution diagonal display is 4096×2048 and typically has viewing distances that are less than 2 picture heights. In order to display a lower resolution image on a higher resolution display, the lower resolution image is upscaled. Large high resolution displays viewed at close viewing distances tend to have annoying artifacts as a result of the upsampling. In addition, due to the limited information in the original video content this upsampling tends to result in noise.
One type of upscaling technology involves an edge adaptive spatial filter technique that locates the edges and contours within the incoming image and controls the filtering process near the edges. These techniques can produce an upsampled image with sharp natural looking edge contours. However, edge adaptive upsampling techniques tend to blur textures. Another drawback of edge adaptive techniques is that they can mistake non-edge features for edges as a result of edge classification. This introduces local spurious edges that are not in the original, and that are very easily observed as mistakes.
Another type of image modification technique that may be used to improve the quality of the perceived image is a sharpening technique, such as an unsharp mask. The unsharp mask increases the apparent sharpness of an image by using a blurred positive to create a mask of the original image. The unsharp mask is then combined with the negative to create the illusion that the resulting image is sharper than the original. In general, the unsharp masks amplifies the higher frequency components of the image.
Another type of image modification technique that may be used to improve the quality of the perceived image is a noise reduction technique. The noise reduction may be achieved using a low-pass smoothing filter. Unfortunately, the smoothing filter tends to blur the image, so non-linear noise reduction filters may be preferred to reduce the blurring. Other types of filters include an anisotropic diffusion filter and a median filter.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings